Robin - as there is no legal requirement for insurance, the insurance company can not effectivelty stipulate any minimums as they are very likely to lose business. You can phone around all the brokers in the back of Pilot magazine and you will find that there are only very few underwriters that will write aviation business. Effectively it is the brokers not the insurers who attempt to stipulate a set of requirements and as the market is very small and they all know each other, they can very effectively be played against each other.
What they may do is increase the excess for the first n hours.
Were this a Pitts or a YAK50 or a C195 then I would be a little more concerned for Tyro and the aircraft but because it's a low powered taildragger that really will only fly when the conditions are perfect, I don't feel the need to worry. If he breaks it, it will be repairable - if he hurts himself it will probably be minor.
A few circuits as previously stated then off he should go.
Stik